Public domain software comes into being when the original copyright holder explicitly relinquishes all rights to the software. Since under current copyright law, all intellectual works (including software) are protected as soon as they are commited to a medium, for something to be public domain it must clearly be marked as such. Before March 1, 1989, it was assumed that intellectual works were NOT covered by copyright unless the copyright symbol and declaration appeared on the work. With the U.S. adherence to the Berne Convention this presumption hasbeen reversed. Now all works assume copyright protection unless the public domain notification is stated. This means that for public domain software
- copyright rights have been relinquished,
- software copies can be made for both archival and distribution purposes with no restrictions as to distribution,
- modifications to the software are allowed,
- decompiling (i.e. reverse engineering) of the program code is allowed, and
- development of new works built upon the package (derivative works) is allowed without conditions on the distribution or use of the derivative work.